Heterogeneity within the native range: population genetic analyses of sympatric invasive and noninvasive clades of the freshwater invading copepodEurytemora affinis

Abstract

Invasive species are often composed of highly differentiated populations or sibling species distributed across their native ranges. This study analysed patterns of distribution and the evolutionary and demographic histories of populations within the native range of the copepod species complex Eurytemora affinis. Genetic structure was analysed for samples from 17 locations from both the invaded and native ranges in the St Lawrence River drainage basin, using 652 base pairs of the mitochondrial cytochrome oxidase subunit I gene. This study revealed a high degree of heterogeneity in genetic structure and habitat type in the native range, as well as a bias in the sources of invasive populations. Two genetically distinct clades showed a pattern of niche partitioning within the St Lawrence basin. The noninvasive North Atlantic clade primarily occupied the central portion of the St Lawrence Middle Estuary, whereas the invasive Atlantic clade was more prevalent along the margins, in the upstream reaches of the estuary and downstream salt marshes. Habitat partitioning and genetic subdivision was also present within the Atlantic clade. The freshwater populations were genetically more proximate to the Atlantic clade populations in the estuary than to those in the salt marsh, suggesting the estuary as the source of the invasive populations. The freshwater invading populations showed evidence of a modest population bottleneck. Populations from both clades showed genetic signatures of demographic population expansions that preceded the timing of the last glacial maximum, supporting the St Lawrence as a secondary contact zone between the two clades. Additional analyses on physiological and evolutionary properties of populations in the native range, along with analysis of the selection regime within native habitats, might yield insights into the evolutionary potential to invade.

Biological invasions and natural colonisations: are they that different?

“…We agree that higher propagule pressure increases the likelihood of colonisation success (Blackburn et al 2013) and also that more important than genetic diversity is the presence of genes suitable for movement to novel locations (Lee 2002;Winkler et al 2008) and in some instances, genetic admixture (Rius and Darling 2014). Indeed, for species dispersed by either natural or human-mediated transport, and regardless of whether the dispersal is within a region or across a geographic barrier, often only a subset of a species' genetic pool can colonise new locations.…”

Phenotypic Plasticity Promotes Balanced Polymorphism in Periodic Environments by a Genomic Storage Effect

“…However, natural populations that experience a seasonal succession of generations might be much larger than the one simulated here, N = 10 5 (for example, Winkler et al 2008). This is particularly true since the population size relevant to allele frequencies is not simply the effective population size shaped by demographic history involving bottlenecks, but a typically larger "short-term" effective population size during which adaptation occurs (Karasov et al 2010).…”

When anthropogenic translocation meets cryptic speciation globalized bouillon originates; molecular variability of the cosmopolitan freshwater cyclopoidMacrocyclops albidus(Crustacea: Copepoda)

“…If proven in further studies, this would indicate that they probably exclude each other by competing for the same resources, and that their original (pre-anthropogenic) distribution was allopatric. These are indeed handy properties for experimental studies on invasive species, and copepod crustaceans are ideal experimental organisms due to their small size, short generation time and easy maintenance (Winkler et al, 2008). Whereas phylogenetic analyses can show the direction of niche shifts (best known on oceanic islands), we do not really understand how a population may enter a new habitat or exploit new resources, persist for many generations in the face of abiotic and biotic pressures to which it is not well adapted, and undergo genetic and phenotypic changes that enhance fitness and correlatively render it a new species (Abbott et al, 2003).…”

“…Subsequent records include that of one Afro-Asian cyclopoid species in the Cayman Islands by Suarez-Morales et al (1999), two Asian calanoids and one cyclopoid in the San Francisco Estuary by Orsi and Ohtsuka (1999), two Ponto-Caspian harpacticoids in the nearshore sands of Lake Michigan by Horvath et al (2001); one tropical calanoid in Japan by Ohtsuka et al (2005); and possibly one brackish cyclopoid in Western Australia (Karanovic, 2008). A particularly well-studied example is that of the calanoid copepod Eurytemora affinis (Poppe, 1880), which exhibited rapid and repeated invasions of freshwater from brackish and marine habitats (Lee, 1999;Lee et al, 2003Lee et al, , 2007Winkler et al, 2008). Ballast water is today recognized as a major vector of nonindigenous species invasion globally (Grey et al, 2007;Zvyaginstev and Selifonova, 2008), and many management options have been developed so far (for a review, see Gregg et al, 2009).…”